Applying a total energy absorption γ-ray detector composed of 12 bricks (5×5cm², 7.5cm thick) of BGO scintillators, the absolute measurement of capture cross sections for Au and Sb has been made in an energy region between 0.01 and 10eV using the linac time-of-flight method. Incident thermal neutron flux was absolutely determined by using the BGO detection system with a Sm sample. T6 extend the neutron flux measurement from the thermal neutron region to higher neutron energies, the ¹⁰B(n, αγ) reaction was applied. Absolute capture yield for the relevant capture sample was obtained by the saturated capture yield at a large resonance of the sample.
Gold was selected to investigate the application of the BGO detection system to the absolute measurement of the capture cross sections, since the ¹⁹⁷Au(n, -γ)¹⁹⁸Au reaction cross section is a well known standard one.The result of the ¹⁹⁷Au(n, -γ)¹⁹⁸Au reaction cross section showed good agreement with the evaluated data in JENDL Dosimetry File and ENDF/B-VI. Then, the detection system was applied to the Sb(n, γ) cross section measurement. Antimony has a large scattering-to-capture cross section ratio comparing to that of gold. Theresult showed good agreement with the evaluated data in JENDL-3.2 and ENDF/B-VI.

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A heat transfer and flow visualization experiment was conducted with a one-fifth scale model simulatinga dry shielded canister (DSC) with 24 PWR spent fuel assemblies in order to elucidate the heat transfer characteristics and the velocity distribution for natural convection inside a DSC filled with air or water at atmospheric pressure. It was found that the average heat transfer coefficients were proportional to the onefourth power of the Rayleigh number despite the complicated geometry inside the DSC. Flow patterns inside the DSC were visualized clearly through a digital image processing system. The velocity distributions inside the DSC were obtained quantitatively from the Particle Tracking Velocimetry. In comparison with the results of a two-dimentional thermal hydraulic analysis, computed flow patterns were similar to the experimental results and the computational temperature distributions on the sleeve surfaces agreed well with the experiments within 8%, except at the top point of the center gap. It was also found that the difference in the heat transfer coefficient was within 25% for air as the working fluid, while a satisfactory agreement was not obtained when water was the working fluid.

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The oxidation behavior of Zr2(Fe, Ni) precipitate in Zircaloy-2 was examined by microprobe Auger electron analysis focussing attention on the oxidation behavior of iron and nickel. In the pre-transition period, the iron oxide was formed only on the top surface of zirconium oxide layer of the precipitate and the thickness of iron oxide layer increased with the oxidation time, and nickel was oxidized via dissolution in the matrix zirconium oxide near the top surface. In the post-transition period, the oxidation of iron and nickel proceeded also inside the oxide layer. Such variety of oxidation behavior of iron and nickel between the pre- and post-transition period was attributed to the situation whether the oxygen potential gradient existed or not in the matrix zirconium oxide layer.

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Ions were collected on electrodes from laser resonance photoionized plasma by applying 2MHz radiofrequency voltage to the electrodes. It was demonstrated that the ions are collected in a shorter time at the same kinetic energy of the collected ions compared with ion collection by applying DC voltage to the electrode. A simple one-dimensional model was extended for prediction of ion collection times in the cases of applications of not only DC voltage but also radio-frequency voltage. The ion collection times estimated with the simple one-dimensional model agreed with the experimental values in the case of application of radiofrequency voltages as well as DC voltage. Though the experimental conditions such as ion density are far from those of the plant of atomic vapor laser isotope separation (AVLIS), the simple one-dimensional model shows that radio-frequency voltage method is effective under the conditions close to those of the AVLIS plant.

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The adsorption behavior of Cs onto quartz was investigated with the use of a high performance liquid chromatograph. The surface-based distribution coefficient (Ka) of Cs onto quartz was determined in the solution of which pH ranged from 6 to 11 and ionic strength from 10^-3 rvt to 10^-1M. The Ka values were found to increase with increasing pH and with decreasing ionic strength. The obtained data were successfully analyzed by an electrical double layer model and the optimum parameter values of the double layer electrostatics and adsorption reactions were obtained. The adsorption mechanisms of alkali metal ions was discussed on the basis of the present analysis.

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The adsorption of Eu(III) and Co(II) on laboratory-prepared amorphous hydrous iron and aluminum oxides, goethite and gibbsite, was studied as a function of pH over a wide range of metal ion concentrations, in order to see the effect of the change in the degree of site occupation by metal ions. When the metal ion concentrations were low, a simple Langmuir equation with a single adsorption constant was able to describe adsorption on these hydrous oxides. At high metal ion concentrations, adsorption on goethite and gibbsite exhibited clear saturation maxima expected from a simple one-to-one interaction between the metal ion and the adsorption site, while adsorption on laboratory-prepared hydrous oxides continued to increase gradually even at high metal ion concentrations.

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After their land disposal, LiNO3 added to cement solidified miscellaneous wastes inhibits hydrogen gas generation due to alkaline corrosion of aluminum contained in the wastes. We considered the presence of an Li-Al preservation film prevents hydrogen gas generation, and then, we assumed a scenario in which the amount of LiNO3 included in the waste packages is lowered by underground water penetration, resulting in dissolution of the Li-Al preservation film. This dissolution allows the alkaline underground water to reach and corrode the aluminum materials. The loss of Na₂O and K₂O in cement by underground water penetration lowers the pH, so that the aluminum corrosion in the waste packages with LiNO₃, expected when the Li-Al preservation film dissolves, is less than that without LiNO₃.
To test this scenario, we measured solubility of the Li-Al preservation film, L⁺ ion concentration, pH variation by underground water penetration, and aluminum corrosion when the Li-Al preservation film had dissolved. The measured solubility of the Li-Al preservation film was 3×10^-4M at 283K. At that time, pH was lowered from 12.9- 13.0 to 12.2-12.3. As a result, with LiNO3 addition the aluminum corrosion amount was reduced to 10% of that without LiNO3 addition, because of the pH decrease.

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The variance-to-mean ratios of counts accumulated during a time-gate were measured as a function of gate width for several Geiger-Mueller(GM) and neutron proportional counters. The measured ratios asymptotically decreased with an increase in gate width. The ratio for a GM counter was saturated in about 400μs of gate width, while that for a neutron counter was done in about 40μs. Applying the first- and second-order formulae derived from the Muller's expression for the variance-to-mean ratio, the dead times of these counters were inferred from these saturated ratios. In the count-rate range above 1, 000cps for the GM counter and above 12, 000cps for the neutron counter, the dead times obtained by the first-order formula apparently depended on count rate. On the contrary, the application of the second-order formula sufficiently reduced the count-rate dependence. The dead times obtained by the second-order formula were consistent with those by the previous two-source or reactor-power variational methods.

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Installation and replacement of many PWR-steam generators are planned inside and outside Japan. The steel plates for steam generators are heavy in thickness, and increase the number of welding passes and prolong the welding time Electron beam welding (EBW) can greatly reduce the welding period compared with conventional welding methods (narrow-gap gas metal arc welding (GMAW) and submerged arc welding (SAW)). The problems in applying EBW are to prevent weld defects and to improve the toughness of the weld metal. Defect-free welding procedures were successfully established even in thick steel plates. The factors that deteriorate weld-metal (WM) toughness of EBW were investigated. The manufacturing process, which utilizes a new secondary refining process at steelmaking and a high-torque mill at plate mill in actual mass-production, were established. EBW base metal and WM have better properties including fracture toughness than those of conventional welding processes. As a result, an application of EBW to the fabrication of PWR-steam generators has become possible. Large amounts of ASTM A533 Gr B Cl 2 (JIS SQV2B) steel plates in actual PWR-steam generators have come to be produced (more than 1, 500ton) by appling EBW.

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The process constituting the elements of the method for treating high-level liquid waste with addition of reducing agent at temperatures above 1, 873K were examined applying thermogravimetry and X-ray diffractometry to sample mixtures of the platinum metal oxides RuO₂, Rh₂O₃, PdO and of Re₂O₇, with and without addition of TiN as reducing agent. The addition of TiN reducing agent proved to induce reduction of the platinum metal oxides at temperatures far below those of thermal decomposition occurring in the absence of reducing agent. The presence of reducing agent further proved to reduce Re₂O₇ to ReO₃ at 373K, to ReO₂ at 773K and to Re metal at 1, 073K. At around 773K disproportionation reconverted part of the ReO₃ formed at 373K to ReO₂ and Re₂O₇. Thus, sublimation of the Re₂O₇ in starting material which occurs at 523K in the absence of TiN was eliminated, and occurred only at 773K on the Re₂O₇ that was regenerated at that temperature by disproportionation of the converted ReO₃. Alloys of Ru, Rh and Pd resulting from the above treatment with TiN proved to agree with what is indicated from phase diagrams. Among the alternative compounds existing in the Rh-Ti and Rh-Ti binary systems, however, solely Ru-Ti proved to have been produced.

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